T_DOLLAR_OPEN_CURLY_BRACES should handle EXPR

This syntax should be valid :

```php
<?php
echo "hello ${foo()} ";
```

- Syntax : https://github.com/php/php-src/blob/master/Zend/zend_language_parser.y#L1244
- Implementation : https://github.com/glayzzle/php-parser/blob/master/src/parser/scalar.js#L185

---

Actual output : 
```
Parse Error : syntax error, unexpected 'foo()} ' (T_ENCAPSED_AND_WHITESPACE) on line 2
```